Post-Closure RCRA Groundwater Monitoring Plan for the 216-S-10 Pond and Ditch PDF Download

Author: D. BRENT. Barnett
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Languages : en
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Book Description
The purpose of this plan is to provide a post-closure groundwater monitoring program for the 216-S-10 Pond and Ditch (S-10) treatment, storage, and/or disposal (TSD) unit. The plan incorporates the sum of knowledge about the potential for groundwater contamination to originate from the S-10, including groundwater monitoring results, hydrogeology, and operational history. The S-10 has not received liquid waste since October 1991. The closure of S-10 has been coordinated with the 200-CS-1 source operable unit in accordance with the Tri-Party Agreement interim milestones M-20-39 and M-15-39C. The S-10 is closely situated among other waste sites of very similar operational histories. The proximity of the S-10 to the other facilities (216-S-17 pond, 216-S-11 Pond, 216-S-5,6 cribs, 216-S-16 ditch and pond, and 216-U-9 ditch) indicate that at least some observed groundwater contamination beneath and downgradient of S-10 could have originated from waste sites other than S-10. Hence, it may not be feasible to strictly discriminate between the contributions of each waste site to groundwater contamination beneath the S-10. A post-closure groundwater monitoring network is proposed that will include the drilling of three new wells to replace wells that have gone dry. When completed, the revised network will meet the intent for groundwater monitoring network under WAC 173-303-645, and enable an improved understanding of groundwater contamination at the S-10. Site-specific sampling constituents are based on the dangerous waste constituents of concern relating to RCRA TSD unit operations (TSD unit constituents) identified in the Part A Permit Application. Thus, a constituent is selected for monitoring if it is: A dangerous waste constituent identified in the Part A Permit Application, or A mobile decomposition product (i.e., nitrate from nitrite) of a Part A constituent, or A reliable indicator of the site-specific contaminants (i.e., specific conductance). Using these criteria, the following constituent list and sampling schedule is proposed: Constituent; Sampling Frequency Site-Specific Parameters; Hexavalent chromium (a); Semiannual Chloride; Semiannual Fluoride; Semiannual Nitrate; Semiannual Nitrite; Semiannual Specific conductance (field)(a); Semiannual Ancillary Parameters; Anions; Annual Alkalinity Annual Metals, (in addition to chromium); Annual pH (field) Semiannual Temperature (field); Semiannual Turbidity (field) Semiannual (a). These constituents will be subject to statistical tests after background is established. It will be necessary to install new monitoring wells and accumulate background data on the groundwater from those wells before statistical comparisons can be made. Until then, the constituents listed above will be evaluated by tracking and trending concentrations in all wells and comparing these results with the corresponding DWS or Hanford Site background concentration for each constituent. If a comparison value (background or DWS) for a constituent is exceeded, DOE will notify Ecology per WAC 173-303-645 (9) (g) requirements (within seven days or a time agreed to between DOE and Ecology).